This invention relates to fluid drop dispensing devices and methods for the manufacture of such devices. More particularly, it concerns droplet dispensing devices intended primarily, though not exclusively, for use in ink jet printers and to the method for forming and assembling the components thereof.
Commonly assigned U.S. Pat. No. 4,550,325 issued on Oct. 29, 1985 discloses a fluid drop dispenser in which a circular piezoelectric actuator disk is oriented concentrically with an annular fluid receiving chamber in a manner such that when the disk is electrically excited, it expands radially to compress the annular chamber and expel a drop of the fluid through a nozzle in an exterior wall of the chamber. Apart from the piezoelectric disk, the device disclosed in the aforesaid patent is constructed entirely from injection moldable plastic parts constituted primarily by inner and outer ring-shaped members. The outer ring supports a drop dispensing nozzle and defines a relatively rigid or fixed inwardly facing cylindrical wall surface to establish the outer surface of the annular chamber. The inner ring telescopes within the outer ring and is formed with a relatively thin cylindrical wall portion engaged on its inner surface by the piezoelectric disk and having its outer surface spaced from the inner surface of the outer ring by the radial dimension of the annular chamber. The two rings are secured to each other to maintain their assembled condition and also to render the annular chamber fluid tight by solvent or adhesive bonding or by ultrasonic fusion. Also the outer peripheral surface of the electroactuator disk is secured by an adhesive to the inner surface of the inner ring in the region of the relatively thin flexible wall thereof.
While drop dispensers of the type disclosed in the aforementioned patent have demonstrated considerable potential for highly effective use in ink jet printers as well as in other precisely controlled drop dispensing applications, and may be manufactured very inexpensively as a result of component formation by injection molding, the requirements for bonding or otherwise fusing the plastic parts is relatively tedious and presents a problem particularly in light of the extremely small size of the assembled dispenser. Extreme care must be taken in the bonding or fusion parts to insure complete sealing of inter-fitting surfaces without distorting operating surface portions which have an effect on the drop formation to be discharged each time the electroactuator disk is excited. Accordingly, there is a need for improvement particularly in the solution of problems associated with fusion of the assembled dispenser components.